Resonant inverters, which are an example of discharge generators, are configured to cause a discharge load, such as an ozonizer, to generate discharge. An example of which is disclosed in Japanese Patent Publication No. 4108108. Such a resonant inverter includes a main circuit unit including switching elements, and a control unit.
The control unit controls on-off switching operations of each switching element to thereby convert an input direct-current (DC) voltage input from a DC power source into an alternating-current (AC) voltage. Then, the resonant inverter outputs the AC voltage to a resonant circuit while causing a switching frequency of each switching element to resonate with a predetermined resonant frequency of a resonant circuit including a discharge load, thus applying a boosted AC voltage to the discharge load. This causes the discharge load to generate discharge.
Such a discharge load has a discharge start voltage as its one characteristic. The discharge start voltage represents a minimum voltage required for the discharge load to generate discharge. Note that power required for the discharge load to generate discharge will also be referred to as discharge start power. If output power supplied from the main circuit unit to the discharge load is lower than the discharge start power, no discharge is generated by the discharge load.